Microelectronic devices are fabricated on and/or in microelectronic workpieces using several different apparatus (“tools”). Many such processing apparatus have a single processing station that performs one or more procedures on the workpieces. Other processing apparatus have a plurality of processing stations that perform a series of different procedures on individual workpieces or batches of workpieces. The workpieces are often handled by automatic handling equipment (i.e., robots) because microelectronic fabrication requires very precise positioning of the workpieces and/or conditions that are not suitable for human access (e.g., vacuum environments, high temperatures, chemicals, stringent clean standards, etc.).
An increasingly important category of processing apparatus are plating tools that plate metals and other materials onto workpieces. Existing plating tools use automatic handling equipment to handle the workpieces because the position, movement and cleanliness of the workpieces are important parameters for accurately plating materials onto the workpieces. The plating tools can be used to plate metals and other materials (e.g., ceramics or polymers) in the formation of contacts, interconnects and other components of microelectronic devices. For example, copper plating tools are used to form copper contacts and interconnects on semiconductor wafers, field emission displays, read/write heads and other types of microelectronic workpieces. A typical copper plating process involves depositing a copper seed layer onto the surface of the workpiece using chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating processes, or other suitable methods. After forming the seed layer, copper is plated onto the workpiece by applying an appropriate electrical field between the seed layer and an anode in the presence of an electrochemical plating solution. The workpiece is then cleaned, etched and/or annealed in subsequent procedures before transferring the workpiece to another apparatus.
Single-wafer plating tools generally have a load/unload station, a number of plating chambers, a number of cleaning chambers, and a transfer mechanism for moving the microelectronic workpieces between the various chambers and the load/unload station. The transfer mechanism can be a rotary system having one or more robots that rotate about a fixed location in the plating tool. One existing rotary transfer mechanism is shown in U.S. Pat. No. 6,136,163 issued to Cheung, et al. Alternate transfer mechanisms include linear systems that have an elongated track and a plurality of individual robots that can move independently along the track. Each of the robots on a linear track can also include independently operable end-effectors. Existing linear track systems are shown in U.S. Pat. No. 5,571,325 issued to Ueyama, et al., PCT Publication No. WO 00/02808, and U.S. patent application Ser. Nos. 09/386,566; 09/386,590; 09/386,568; and 09/759,998, all of which are herein incorporated in their entirety by reference. Many rotary and linear transfer mechanisms have a plurality of individual robots that can each independently access most, if not all, of the processing stations within an individual tool to increase the flexibility and throughput of the plating tool.
These robots use end-effectors to carry the workpiece as it moves from one processing station to another. The nature and design of the end-effectors will depend, in part, on the nature of the workpiece being handled. For example, when the backside of the workpiece may directly contact the end-effector, a vacuum-based end-effector may be used. Such vacuum-based end-effectors typically have a plurality of vacuum outlets that draw the backside of the workpiece against a paddle or other type of end-effector. In other circumstances, however, the workpieces have components or materials on both the backside and the device side that cannot be contacted by the end-effector. For example, workpieces that have wafer-level packaging have components on both the device side and the backside. Such workpieces typically must be handled by edge-grip end-effectors, and the distance radially inward from the edge of a workpiece that such edge-grip end-effectors may contact is very limited. This makes it more difficult to securely grasp the workpiece during handling.
Several current edge-grip end-effectors use an active member that moves in the plane of the workpiece between a release position and a processing position to retain the workpiece on the end-effector. In the release position, the active member is disengaged from the workpiece in a position that is spaced apart from the workpiece to allow loading/unloading of the end-effector. In the processing position, the active member presses against the edge of the workpiece to drive the workpiece laterally against other edge-grip members in a manner that secures the workpiece to the end-effector. The active member can be a plunger with a groove that receives the edge of the workpiece, and the other edge-grip members can be projections that also have a groove to receive other portions of the edge of the workpiece. In operation, the active member moves radially outward to the release position to receive a workpiece and then moves radially inward to the processing position to securely grip the edge of the workpiece in the grooves of the edge-grip members and the active member.
One concern of active edge-grip end-effectors is that they have several moving components that increase the complexity of manufacturing and servicing. For example, the mechanical or electrical systems that drive the active member can fail, which causes downtime or damage to workpieces. Additionally, contaminants can build up in small gaps and recesses in plunger-type active members. Therefore, active edge-grip end-effectors may not be suitable for use in certain types of integrated plating tools.
It would also be advantageous to confirm that a workpiece is properly positioned on an end-effector before the end-effector moves the workpiece. International Publication No. WO 00/02808 suggests using light reflected off the workpiece to determine the presence of a workpiece. A lack of reflected light indicates that no workpiece is present. While such a system does indicate whether a workpiece is in the proper vicinity, it does not ensure that the workpiece is properly seated on the end-effector. Thus, semiconductor fabricators also need better systems for determining whether a workpiece is in the correct position on edge-grip end-effectors. The proper positioning of the workpiece on edge-grip end-effectors is particularly important because the edge-grip members must also space the workpiece apart from the paddle.